Wondimagegnehu Mersie

Phenolic acids affect photosynthesis and protein synthesis by isolated leaf cells of velvet-leaf

The effects ofp-coumaric, ferulic, chlorogenic, and vanillic acids on photosynthesis and protein synthesis by isolated leaf cells of velvetleaf (Abutilon theophrasti Medik) were investigated. Photosynthesis and protein synthesis were measured in cell suspensions by the incorporation of14CO2 and [14C]leucine, respectively. None of the tested phenolic acids except vanillic reduced photosynthesis by more than 50% at the highest concentration and 30 min of incubation. At 100μM concentrations and 60-min incubation periods,p-coumaric, ferulic, chlorogenic, and vanillic acids inhibited photosynthesis by 33, 37, 57, and 65%, respectively. Ferulic acid was the most inhibitory to protein synthesis and reduced the incorporation of [14C]leucine by 50% at about 1.0μM after 60 min of incubation. At the highest concentrations tested in this study, vanillic and ferulic acids were inhibitory to photosynthesis and protein synthesis, respectively, whereas chlorogenic andp-coumaric acids did not inhibit either physiological process. The maximum inhibition of protein synthesis by chlorogenic acid was 19% and by vanillic acid was 28% at 100μM concentrations. Chlorogenic, vanillic, andp-cou-maric acids at 0.1μM caused increased protein synthesis over the untreated control. Overall, photosynthesis was more sensitive than protein synthesis to the four phenolic acids tested.

Allelopathic effect of lantana on some agronomic crops and weeds

SummaryThe allelopathic effects of dried lantana shoot residues was examined on wheat, corn, soybean, Virginia pepperweed and velvetleaf on growth over a 30-day period. Significant differences in the growth of the test species were observed. Corn was the most sensitive and wheat was least affected by lantana residues. The other three species were intermediate in their growth response to lantana. Shoot lengths were affected in corn and velvetleaf while root length was reduced in all species except wheat. The shoot dry weights of wheat and soybean were not reduced by lantana residues. In the other three species there was a significant reduction of shoot dry weight due to lantana. The root dry weights of all the five species were reduced by lantana residue. The results demonstrated an overall rate dependent response of the plant species to lantana shoot residue concentrations.

Phytotoxicity of the Fungicide Metalaxyl and Its Optical Isomers

Metalaxyl is a systemic fungicide commonly used in citrus production to control Phytophthora root rot and foot rot. When applied as a drench, injury was observed on newly planted, young citrus trees. The visual injury symptoms ranged from light- to bright-yellow leaves. It was learned that the commercial formulation of metalaxyl contained various isomers and that these isomers may vary in phytotoxic effects on citrus leaves. The objective of this study was to determine the difference in herbicidal activity between the two optical isomers of metalaxyl on pepper plants and citrus leaves. The phytotoxicity of the fungicide metalaxyl and its optical isomers (CGA76538, S+; CGA76539, R-) was determined using a pepper seedling growth bioassay and by measuring protein synthesis as estimated by the incorporation of 14C-leucine by citrus mesophyll cells. The two isomers and metalaxyl differed in their herbicidal activity to pepper plants and citrus cells. Pepper seedlings treated with R- had significantly higher mean fresh weight than plants treated with metalaxyl or S+ at 0.1, 1.0, 10.0, and 100 ppm. Protein synthesis, as measured by the inhibition of 14C-leucine incorporation by citrus mesophyll cells, also was inhibited more by metalaxyl and the S+ isomer than by the R- isomer. After 30 min of incubation at 100 μM, the R- isomer inhibited 14C-leucine incorporation by 29%, whereas incorporation of 14C-leucine in the metalaxyl and the S+ isomer treatments was higher (46 and 81%, respectively). Similarly, the highest 14C-leucine uptake at 60 min was obtained by R- at all concentrations. The assays showed that the R- and S+ isomers differ in their biological activity as expressed by weight loss of pepper plants and inhibition of protein synthesis and that the S+ isomer is responsible for the phytotoxicity of metalaxyl. The findings in this study show that the phytotoxicity of metalaxyl was due to the presence of the S+ optical isomer. Removal of this isomer from metalaxyl has enabled the continued use of this fungicide for control of foot rot and root rot in citrus.

Comparison of norflurazon absorption by excised roots of three plant species

Abstract The absorption of norflurazon by 1-cm segments cut from the apical 5-cm roots of sicklepod ( Cassia obtusifolia L.), corn ( Zea mays L. cv. Sunbelt 1860), and cotton ( Gossyipium hirsutum L. cv. DPL 90) was investigated. Norflurazon absorption by all root tissues was rapid in the first 10 min but there was very little increase thereafter up to 60 min. Norflurazon also penetrated the entire root tissue volume within 30 min, indicating its movement into both the apoplast and the symplast of root cells by simple diffusion. The initial (0–10 min) rate of norflurazon absorption was faster in sicklepod and cotton than in corn. Corn also accumulated less 14 C than did the other species. Norflurazon diffused freely out of sicklepod and corn root tissues but not out of cotton roots. Metabolism was not the basis for this differential retention as norflurazon was not degraded by the root tissues over a 24-hr period. These experiments show that differential accumulation and retention of norflurazon by root tissues was not related to the selectivity of this herbicide among these three species.

Absorption, translocation, and metabolism of thuringiensin in potato

The absorption, translocation, and metabolism of the bacterial insecticide,14C-thuringiensin in potato (Solarium tuberosum L.) was investigated. Under controlled-environment conditions (21/18 C, 70/95% day/night), the insecticide was applied to potato leaves at tuber initiation. Potato plants absorbed 19 and 20% of the applied insecticide after 3 and 7 days after treatment. Approximately 79 and 72% of the applied radioactivity was washed from the treated leaf 3 and 7 days after treatment. Of the applied14C-thuringiensin, less than 5% was translocated both at 3 and 7 days after treatment. About 15% of the applied, which was equivalent to 70% of the absorbed remained in the treated leaf. There were no significant differences in the concentration of thuringiensin in different parts of potato at both periods of exposures. The insecticide was not metabolized by potato disks after 24 and 48 hr of exposure. Adequate leaf coverage and frequent application may be necessary to obtain effective control of insects with this compound.CompendioSe ha investigado la absorción, translocación y metabolismo del insecticida bacteriano turingiensina C14 en papa (Solarium tuberosum L.). Se aplicó el insecticida, bajo condiciones controladas (21/18 C, 70/95%, día/noche), a las hojas de papa a la iniciación de la tuberización. Las plantas de papa absorbieron 19 a 20% del insecticida aplicado 3 a 7 días después del tratamiento. Aproximadamente 79 y 72% de la radiactividad aplicada fué eliminada de la hoja tratada a los 3 a 7 días después del tratamiento. De la turingiensina C14 aplicada, menos del 5% se translocó a los 3 y 7 días después del tratamiento. Aproximadamente el 15% de lo aplicado equivalente al 70% de lo absorbido permaneció en la hoja tratada. No hubo diferencias significativas en la concentración de turingiensina en las diferentes partes de la papa en ambos periodos de exposición. El insecticida no fué metabolizado por discos de papa después de 24 a 48 horas de exposición. Puede ser necesaria una adecuada cobertura de la hoja y aplicación frecuente, para obtener un control efectivo de insectos con este compuesto.

Absorption, Translocation, and Metabolism of C-Thuringiensin (@b- Exotoxin) in Snapbeans

The absorption, translocation, and metabolism of ^1^4C-thuringiensin (@b-exotoxin), an insecticide derived from Bacillus thuringiensis, were investigated in snapbean (Phaseolus vulgaris L.). The insecticide was applied to snapbean leaves or roots under controlled environmental conditions. Thuringiensin was absorbed more by roots than shoots. Snapbeans absorbed 12 and 17% of the root-applied thuringiensin after 3 and 7 days of application. Less than 3% of the foliar applied thuringiensin was detected in the whole plant and amounts absorbed at 3 and 7 days were similar. More than 90% of the root absorbed radioactivity remained in the root at both times of harvest. About 77 and 65% of the absorbed ^1^4C-thuringiensin remained in treated leaf after 3 and 7 days of foliar application, respectively. Time did not affect the distribution pattern of root or foliar applied thuringiensin in different parts of snapbeans. In this study, thuringiensin was not readily absorbed by roots or leaves of snapbean and had limited mobility. The insecticide was not also readily metabolized by snapbean leaves after 3 and 7 days of exposures. The practical implications of these results are discussed.